In combustion-powered, fastener-driving tools, a combustible fuel is injected into a combustion chamber and mixed with air so as to define a combustible mixture which, upon being ignited, serves to drive a driving piston to which there is fixedly mounted a fastener-driving member. The fastener-driving member is accordingly driven along an axial path, at which the leading nail fastener, of a collated strip or collated array of nail fasteners, has been predisposed, from its retracted position to its extended position so as to drive and discharge the leading nail fastener, of the collated strip or collated array of fasteners, out from the nailing tool and into an underlying substrate. In order to cyclically advance the leading nail fastener of the collated strip or array of fasteners, so as to predispose the leading nail fastener, of the collated strip or array of fasteners, along the axial drive path of the fastener-driving member, such combustion-powered, fastener-driving tools normally employ fastener-feeding or fastener-advancement mechanisms which are effectively powered by means of exhaust gases which have been generated within the combustion chamber, and wherein a portion of such combustion gases have been diverted into a fastener-advancement or fastener-feeding piston-cylinder assembly. An exemplary fastener-advancement or fastener-feeding piston-cylinder assembly of the aforenoted type is disclosed and illustrated within U.S. Pat. No. 5,558,264 which issued to Weinstein on Sep. 24, 1996.
More particularly, as illustrated within FIGS. 1-3, which correspond to FIGS. 4-6 of the Weinstein patent, a fastener-advancement or fastener-feeding mechanism of the aforenoted type is seen to comprise a fastener-feeding mechanism cylinder 220 and a fastener-feeding mechanism piston 230 which is movably disposed within the fastener-feeding mechanism cylinder 220 between a retracted position as disclosed within FIG. 2 and extended positions as disclosed within FIGS. 1 and 3. The fastener-feeding mechanism cylinder 220 comprises a cylindrical wall 222, a closed end wall 224, and an annular bushing 226 fixed within the open end 228 of the cylindrical wall 222. A piston 230 is movably disposed within the cylinder 222 between a withdrawn or retracted position, as disclosed within FIG. 2, and an advanced or extended position as illustrated within FIGS. 1 and 3. The piston 230 includes a piston rod 232 which is movably guided by means of the annular bushing 226, and a coiled spring 234 is interposed between the piston 230 and the end wall 224 so as to bias the piston 230 and the piston rod 232 toward the advanced or extended position. An O-ring member 236 is seated within an annular groove 238 formed upon the piston 230 so as to provide sealing properties with respect to the cylindrical wall 222.
Still yet further, a feeding claw 240 is pivotally mounted upon the front end portion of the piston rod 232, by means of a pivot pin 242 so as to be alternatively disposed at an operative or engaged position with respect to the nails N disposed within the collated strip or array, or an inoperative or disengaged position with respect to the nails N, and a torsion spring 244 is provided so as to bias the feeding claw 240 toward its operative or engaged position. The feeding claw 240 comprises a pair of notched fingers 246 for effectively grabbing or encompassing the leading one of the nail fasteners N in order to advance or move the same forwardly under the biasing action of the spring 234, and the rear surface 248 of the rearwardly disposed finger 246 comprises a cam surface which permits the feeding claw 240 to effectively cam over the next nail fastener N to be advanced as the feeding claw 240 is pivoted to its inoperative or disengaged position, against the biasing force of the torsion spring 244, in response to the rearward movement of the piston 230 and the piston rod 232 under the influence of gas pressure admitted into the cylinder 222 by means of a conduit 274 which fluidically connects the combustion chamber of the tool to the cylinder 222. A holding claw 250, comprising at least one holding finger 260, is also pivotally mounted adjacent to the collated strip of nails N so as to be alternatively disposed at engaged and disengaged positions with respect to the next nail N disposed within the collated strip of nails N. A coil spring 254, disposed within a socket 258 of the holding claw 250, tends to bias the holding claw 250 toward its engaged position.
While the aforenoted type of fastener-advancement or fastener-feeding mechanism assuredly provides a viably operable system, this particular type of fastener-advancement or fastener-feeding mechanism is obviously only operable in connection with a combustion-powered, fastener-driving tool in view of the fact that a portion of the combustion gases must be diverted from the combustion chamber of the combustion-powered, fastener-driving tool and into the cylinder 222 in order to achieve the rearward stroke movement of the fastener-feeding piston 230, the piston rod 232, and the feeding claw 240 assembly in preparation for the feeding or advancement of a new nail fastener N toward the axial drive path along which the driver member of the combustion-powered, fastener-driving tool is movable. Accordingly, a need exists in the art for new and improved fastener-feeding or fastener-advancing systems which are adapted for use in conjunction with fastener-driving tools which are not combustion-powered and which therefore cannot utilize combustion product gases as the source of motive power for moving the feeding claw or similar mechanism in the desired direction during the operative cyclic feeding or advancing of, for example, a leading nail fastener of a collated strip of nail fasteners.